The present invention relates to cable connections and more particularly to a sealed cable joint for joining fiber optic cables.
Fiber optic cables are deployed across many miles of ocean and other large bodies of water to establish communication networks. Because these fiber optic cables cannot be made and deployed in infinite length, sections of the cables must be attached together to extend across large distances. Cable joints are used to connect fiber optic cables together, for example, when splicing the optical fibers. Although the cable joints are designed to protect the optical fibers and splice connection in a high-pressure, underwater environment, there are a number of cases where additional protection is needed.
In one case, hydrogen may enter the cable joint and adversely affect the optical fibers exposed within the cable joint. The hydrogen is generated near the cable joint from galvanic corrosion of metal parts, magnetohydrodynamic effects, and microbial activity near the connection of the cable with the cable joint. The hydrogen causes optical loss in the optical fiber, which is known in the art as hydrogen induced attenuation. If hydrogen penetrates a significant distance along the optical fibers, then the hydrogen causes a significant amount of hydrogen induced attenuation in the optical fiber.
Previous attempts at sealing cable joints have resulted in seals around every nut and bolt used in the cable joint. Although these existing cable joints may be sealed against water penetration, these cable joints generally are not adequately sealed against the penetration of hydrogen.
One type of seal used in an underwater cable joint to seal against the penetration of hydrogen is disclosed in U.S. Pat. No. 6,028,974. This cable joint includes a casing 130, an anchorage 120, a casing loading ring 150, and an anchorage loading ring 145. A seal ring 140 is positioned between the casing 130 and anchorage 120 and the respective casing loading ring 150 and anchorage loading ring 145. The purpose of the seal ring 140 is to prevent hydrogen from entering the cable junction.
The arrangement disclosed in U.S. Pat. No. 6,028,974, however, has some drawbacks. First, a large amount of force is required to install the seal ring 140. The casing 130 and the anchorage 120 have respective circular ridges 260, 263 for embedding into the seal ring 140. U.S. Pat. No. 6,028,974 discloses an embodiment of the cable junction 100 for an optical fiber cable 110 having a diameter of 14 mm which will require a load of approximately 180 kN to properly embed the circular ridges 260, 263 having sharp leading edges 265, 267 in the seal ring 140. To properly apply this force, it may be necessary to apply an external load with a press machine to embed the circular ridges 260, 263 into the seal ring 140 before tightening the loading rings 145, 150. This additional pressing step and the required force can make assembly of this cable joint difficult. Also, the seal ring 140 is positioned in a gap between the casing 130 and loading ring 150 and is exposed to the outside of the casing 130. Thus, this seal ring 140 may be susceptible to failure.
Accordingly, there is a need for a sealed cable joint that is easier to assemble and stronger than existing seals.
In accordance with one aspect of the present invention, a sealed cable joint connects first and second cables. The sealed cable joint comprises a housing having first and second ends and an inner surface defining an inner region. First and second cable socket bodies are positioned within the inner region of the housing at the first and second ends of the housing. Each of the first and second cable socket bodies includes a passageway receiving respective cables. First and second seal securing members are positioned within the inner region of the housing at the first and second ends of the housing and are secured into contact with the respective socket bodies.
The sealed cable joint also comprises a first seal positioned against the inner surface of the housing at an interface between the first cable socket body and the first seal securing member. A second seal is positioned against the inner surface of the housing at an interface between the second cable socket body and the second seal securing member. The first and second seals are compressed between the respective first and second seal securing members and the respective first and second cable socket bodies for sealing against the housing.
According to one embodiment, each of the cable socket bodies includes a seating portion and a radial portion extending radially from the seating portion. The seal securing members are seated on the seating portion and against the radial portion of the respective cable socket bodies. The radial portion of each of the cable socket bodies includes an outer groove holding the respective seals. In this embodiment, the seal securing member is preferably secured to the housing.
According to another embodiment, each of the seal securing members is secured against an end face of the respective cable socket bodies. The seal securing members preferably include an outer groove holding the respective seals. The sealed cable joint according to this embodiment preferably further comprises at least first and second inner seals. Each of the seal securing members includes an inner groove spaced radially inwardly from the outer groove to hold the respective inner seals. In this embodiment, the socket bodies are preferably secured to the housing.
The preferred embodiment of the seal includes an annular helically-wound spring and at least one lining around the helically-wound spring. According to one preferred embodiment, the sealed cable joint further comprises first and second cable seals positioned around the respective cables and within the passageways in the respective cable socket bodies. The cable seals preferably have an outer conical shape.
In accordance with a further aspect of the present invention, a sealed cable connection is provided comprising a fiber optic cable including at least one optical fiber and at least one protective outer layer and a housing having an inner surface defining an inner region. At least one cable socket body is positioned within the inner region of the housing and includes a passageway receiving the fiber optic cable. At least one seal securing member is positioned within the inner region of the housing and is secured into contact with the socket body. At least one seal is positioned against the inner surface of the housing and between the cable socket body and the seal securing member. The sealed cable connection can be provided as an assembly.
In accordance with a further aspect of the present invention, a cable connection pre-assembly is provided comprising at least one cable socket body including a passageway for receiving a cable. At least one seal securing member is loosely secured to the cable socket body, and at least one seal is positioned between the cable socket body and the seal securing member.
In accordance with yet another aspect of the present invention, a method is provided for sealing a cable joint. The method comprises inserting at least one seal between a seal securing member and a cable socket body and loosely securing the seal securing member to the cable socket body with the seal positioned therebetween, thereby forming a pre-assembly. The pre-assembly is inserted into and secured to a housing, and a cable is secured to the cable socket body. The seal securing member is tightened against the cable socket body to compress the seal against an inside surface of the housing.